Bags of this type are formed of composite material and normally include an outer sheet, typically a sheet of metallized polymer film, an inner sheet of polymer film defining the inner surface of the bag and a thermally insulating intermediate sheet disposed between the outer sheet and the inner sheet. These sheets are folded to form the bottom of the bag and the outer and inner sheets are welded together along the borders. A handle with closing members is normally provided at the level of the mouth.
Bags of this type have relatively small capacities and can tear if loaded excessively.
Thermal bags of this type are described in FR-A-2550768, in FR-A-2587302 and in US-A-2003/0035596.